<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>纯CSS实现圆环动画</title>
	<style type="text/css">
		.wrapper {
		  width: 100px; /* Set the size of the progress bar */
		  height: 100px;
		  position: absolute; /* Enable clipping */
		  clip: rect(0px, 100px, 100px, 50px); /* Hide half of the progress bar */
		}
		/* Set the sizes of the elements that make up the progress bar */
		.circle {
		  width: 80px;
		  height: 80px;
		  border: 10px solid green;
		  border-radius: 50px;
		  position: absolute;
		  clip: rect(0px, 50px, 100px, 0px);
		}

		/* Using the data attributes for the animation selectors. */
		/* Base settings for all animated elements */
		div[data-anim~=base] {
		  -webkit-animation-iteration-count: 1;  /* Only run once */
		  -webkit-animation-fill-mode: forwards; /* Hold the last keyframe */
		  -webkit-animation-timing-function:linear; /* Linear animation */
		}

		.wrapper[data-anim~=wrapper] {
		  -webkit-animation-duration: 0.01s; /* Complete keyframes asap */
		  -webkit-animation-delay: 3s; /* Wait half of the animation */
		  -webkit-animation-name: close-wrapper; /* Keyframes name */
		}

		.circle[data-anim~=left] {
		  -webkit-animation-duration: 6s; /* Full animation time */
		  -webkit-animation-name: left-spin;
		}

		.circle[data-anim~=right] {
		  -webkit-animation-duration: 3s; /* Half animation time */
		  -webkit-animation-name: right-spin;
		}

		/* Rotate the right side of the progress bar from 0 to 180 degrees */
		@-webkit-keyframes right-spin {
		  from {
		    -webkit-transform: rotate(0deg);
		  }
		  to {
		    -webkit-transform: rotate(180deg);
		  }
		}
		/* Rotate the left side of the progress bar from 0 to 360 degrees */
		@-webkit-keyframes left-spin {
		  from {
		    -webkit-transform: rotate(0deg);
		  }
		  to {
		    -webkit-transform: rotate(360deg);
		  }
		}
		/* Set the wrapper clip to auto, effectively removing the clip */
		@-webkit-keyframes close-wrapper {
		  to {
		    clip: rect(auto, auto, auto, auto);
		  }
		}
	</style>
</head>
<body>
	<div class="wrapper" data-anim="base wrapper">
		<div class="circle" data-anim="base left"></div>
		<div class="circle" data-anim="base right"></div>
	</div>
</body>
</html>